Healthcare workers’ (HCW) well-being has a direct effect on patient care. However, little is known about the prevalence and patterns of long-term medical conditions in HCWs, especially those from ethnic minorities. This study evaluated the burden of multiple long-term conditions (MLTCs), i.e. the presence of two or more single long-term conditions (LTCs), among HCWs in the United Kingdom (UK) and variation by ethnicity and migration status. Methods We used baseline data from the UK-REACH cohort study collected December 2020–March 2021. We used multivariable logistic regression, adjusting for demographic, occupational and lifestyle factors to examine the relationship between self-reported LTCs/MLTCs and ethnicity, migration status and time since migration to the UK. Results Of 12,100 included HCWs, with a median age of 45 years (IQR: 34–54), 27% were overseas-born, and 30% were from non-White ethnic groups (19% Asian, 4% Black, 4% Mixed, 2% Other). The most common self-reported LTCs were anxiety (14.9%), asthma (12.2%), depression (10.7%), hypertension (8.7%) and diabetes (4.0%). Mental health conditions were more prevalent among UK-born than overseas-born HCWs for all ethnic groups (adjusted odds ratio (aOR) using White UK-born as the reference group each time: White overseas-born 0.77, 95%CI 0.66–0.95 for anxiety). Diabetes and hypertension were more common among Asian (e.g. Asian overseas, diabetes aOR 2.97, 95%CI 2.30–3.83) and Black (e.g. Black UK-born, hypertension aOR 1.77, 95%CI 1.05–2.99) groups than White UK-born. After adjustment for age, sex and deprivation, the odds of reporting MLTCs were lower in most ethnic minority groups and lowest for those born overseas, compared to White UK-born (e.g. White overseas-born, aOR 0.68, 95%CI 0.55–0.83; Asian overseas-born aOR 0.75, 95%CI 0.62–0.90; Black overseas-born aOR 0.52, 95%CI 0.36–0.74). The odds of MLTCs in overseas-born HCWs were equivalent to the UK-born population in those who had settled in the UK for ≥ 20 years (aOR 1.14, 95%CI 0.94–1.37). Conclusions Among UK HCWs, the prevalence of common LTCs and odds of reporting MLTCs varied by ethnicity and migrant status. The lower odds of MLTCs in migrant HCWs reverted to the odds of MLTCs in UK-born HCWs over time. Further research on this population should include longitudinal studies with linkage to healthcare records. Interventions should be co-developed with HCWs from different ethnic and migrant groups focussed upon patterns of conditions prevalent in specific HCW subgroups to reduce the overall burden of LTCs/MLTCs.